Wavelength converting member and light emitting device

ABSTRACT

A wavelength converting member comprising a first wavelength converting layer containing: a first fluorescent material having a light emission peak wavelength in a range of 620 nm or more and 660 nm or less; a second fluorescent material having a light emission peak wavelength in a range of 510 nm or more and 560 nm or less; and a resin, wherein the average particle diameter, as measured according to a Fisher Sub-Sieve Sizer method, of the first fluorescent material is in a range of 2 μm or more and 30 μm or less, wherein the second fluorescent material comprises a β-SiAlON fluorescent material, the circularity of the β-SiAlON fluorescent material is 0.7 or more, and the volume average particle diameter, as measured according to a laser diffraction scattering particle size distribution measuring method, of the β-SiAlON fluorescent material is in a range of 2 μm or more and 30 μm or less, and wherein the thickness of the first wavelength converting layer is in a range of 50 μm or more and 200 μm or less.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims priority to Japanese Patent Application No.2018-069611, filed on Mar. 30, 2018, and Japanese Patent Application No.2019-057122, filed on Mar. 25, 2019, the entire disclosures of which areincorporated herein by references in their entirety.

BACKGROUND Technical Field

The present invention relates to a wavelength converting member thatconvers the wavelength of light emitted from a light emitting diode(hereinafter also referred to as “LED”) or a laser diode (hereinafteralso referred to as “LD”), and a light emitting device using the same.

Description of Related Art

A light emitting device containing an LED or an LD in combination with afluorescent material has been used for lighting systems, backlights forliquid crystal display devices, and in-car lights, and demands forthinning the light emitting device have been increased. In thisspecification, the “fluorescent material” is used in the same meaning asa “fluorescent phosphor”.

As the light emitting device, for example, Japanese Unexamined PatentPublication No. 2017-188592 discloses a light emitting device using anLED as a light emitting element, in which a wavelength converting memberformed of a sheet-shaped composition containing a fluorescent materialand a resin is arranged in front of the light emitting element. Withsuch demands for thinning the light emitting device, thinning of thewavelength converting member formed in a sheet shape has been alsorequired.

However, in the thinned wavelength converting member, the color tonedeviation readily occurs on each wavelength converting member due to aninfluence of the deviation of the particle shape of the containedspecific fluorescent material or the distribution state thereof.Further, in the light emitting device using such a wavelength convertingmember, the light emitting device of which the color tone is largelydeviated from a desired color tone is readily present amongmass-produced light emitting devices, and thus the production yield ofthe light emitting device tends to be lower.

Accordingly, an embodiment of the present disclosure has an object toprovide a wavelength converting member capable of providing a desiredcolor tone and improving the production yield, and a light emittingdevice using the same.

SUMMARY

Measures for solving the aforementioned problems are as follows. Thepresent disclosure includes the following embodiments.

A first embodiment of the present disclosure relates to a wavelengthconverting member comprising a first wavelength converting layercontaining: a first fluorescent material having a light emission peakwavelength in a range of 620 nm or more and 660 nm or less; a secondfluorescent material having a light emission peak wavelength in a rangeof 510 nm or more and 560 nm or less; and a resin,

wherein the average particle diameter, as measured according to a FisherSub-Sieve Sizer method, of the first fluorescent material is in a rangeof 2 μm or more and 30 μm or less,

wherein the second fluorescent material comprises a β-SiAlON fluorescentmaterial, the circularity of the β-SiAlON fluorescent material is 0.7 ormore, and the volume average particle diameter, as measured according toa laser diffraction scattering particle size distribution measuringmethod, of the β-SiAlON fluorescent material is in a range of 2 μm ormore and 30 μm or less, and

wherein the thickness of the first wavelength converting layer is in arange of 50 μm or more and 200 μm or less.

A second embodiment of the present disclosure relates to a wavelengthconverting member comprising: a second wavelength converting layercontaining a first fluorescent material having a light emission peakwavelength in a range of 620 nm or more and 660 nm or less and a resin;and a third wavelength converting layer containing a second fluorescentmaterial having a light emission peak wavelength in a range of 510 nm ormore and 560 nm or less and a resin,

wherein the average particle diameter, as measured according to theFisher Sub-Sieve Sizer method, of the first fluorescent material is in arange of 2 μm or more and 30 μm or less,

wherein the second fluorescent material comprises a β-SiAlON fluorescentmaterial, the circularity of the β-SiAlON fluorescent material is 0.7 ormore, and the volume average particle diameter, as measured according tothe laser diffraction scattering particle size distribution measuringmethod, of the β-SiAlON fluorescent material is in a range of 2 μm ormore and 30 μm or less, and

wherein the thickness of each of the second wavelength converting layerand the third wavelength converting layer is in a range of 10 μm or moreand 150 μm or less.

A third embodiment of the present disclosure relates to a light emittingdevice comprising a wavelength converting member according to thepresent disclosure and a light emitting element having a light emissionpeak wavelength in a range of 400 nm or more and 480 nm or less.

In accordance with the wavelength converting member and the lightemitting device of the present, light having a desired color tone can beobtained, and the production yield can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing one example of afirst wavelength converting layer contained in a wavelength convertingmember according to the present disclosure.

FIG. 2 is a schematic cross-sectional view showing one example of asecond wavelength converting layer and a third wavelength convertinglayer each contained in a wavelength converting member according to thepresent disclosure.

FIG. 3 is a schematic cross-sectional view showing one example of awavelength converting member according to the present disclosurecontaining a first wavelength converting layer and a translucent layer.

FIG. 4 is a schematic cross-sectional view showing one example of awavelength converting member according to the present disclosurecontaining a second wavelength converting layer, a third wavelengthconverting layer, and a translucent layer.

FIG. 5 is a schematic perspective view showing one example of a lightemitting device according to the present disclosure.

FIG. 6 is a schematic cross-sectional view showing one example of alight emitting device according to the present disclosure.

FIG. 7 is a schematic cross-sectional view showing another example of alight emitting device according to the present disclosure.

FIG. 8 is a scanning electron microscope (SEM) micrograph showing aβ-SiAlON fluorescent material contained in a wavelength convertingmember according to Example 1.

FIG. 9 is a SEM micrograph showing a β-SiAlON fluorescent materialcontained in a wavelength converting member according to Example 3.

FIG. 10 is a SEM micrograph showing a β-SiAlON fluorescent materialcontained in a wavelength converting member according to ComparativeExample 1.

DETAILED DESCRIPTION

Embodiments of the wavelength converting member and the light emittingdevice according to the present disclosure are hereunder described. Theembodiments shown below are exemplifications for exemplifying thetechnical idea of the present invention, and the present invention isnot limited to the wavelength converting member and the light emittingdevice mentioned below. Standards according to JIS Z8110 are applied tothe relations between color names and chromaticity coordinates, therelations between wavelength ranges of light and color names ofmonochromatic lights.

Wavelength Converting Member

The wavelength converting member is a wavelength converting membercomprising a first wavelength converting layer containing: a firstfluorescent material having a light emission peak wavelength in a rangeof 620 nm or more and 660 nm or less; a second fluorescent materialhaving a light emission peak wavelength in a range of 510 nm or more and560 nm or less; and a resin, wherein the average particle diameter, asmeasured according to the Fisher Sub-Sieve Sizer method (hereinafteralso referred to as “FSSS method”), of the first fluorescent material isin a range of 2 μm or more and 30 μm or less, wherein the secondfluorescent material comprises a β-SiAlON fluorescent material, thecircularity of the β-SiAlON fluorescent material is 0.7 or more, and thevolume average particle diameter, as measured according to the laserdiffraction scattering particle size distribution measuring method, ofthe β-SiAlON fluorescent material is in a range of 2 μm or more and 30μm or less, and wherein the thickness of the first wavelength convertinglayer is in a range of 50 μm or more and 200 μm or less.

The FSSS method is a method of measuring a specific surface area byutilizing the flow resistance of air according to an air permeabilitymethod to determine a particle diameter. The average particle diameter,as measured according to the FSSS method, of particles is also referredto as a Fisher Sub-Sieve Sizer's number. The laser diffractionscattering particle size distribution measuring method is a method ofmeasuring a particle diameter irrespective of primary particles andsecondary particles by utilizing the scattered light from the laserlight radiated to particles. The volume average particle diameter meansan average particle diameter (median diameter: Dm) where the volumecumulative frequency from the small diameter side reaches 50% in thevolume-based particle size distribution, as measured according to thelaser diffraction scattering particle size distribution measuringmethod.

FIG. 1 is a schematic cross-sectional view showing one example of awavelength converting member 50. As shown in FIG. 1, the wavelengthconverting member 50 contains a first wavelength converting layer 51.The first wavelength converting layer 51 contains two kinds offluorescent materials, including a first fluorescent material 61 and asecond fluorescent material 62. The first wavelength converting layer 51converts excitation light emitted from a light emitting element to lighthaving a different wavelength by the first fluorescent material 61 andthe second fluorescent material 62, so that mixed-color light having adesired color tone can be provided. The first wavelength convertinglayer 51 contains the first fluorescent material 61, the secondfluorescent material 62, and a resin 54. The thickness of the firstwavelength converting layer 51 is in a range of 50 μm or more and 200 μmor less, and preferably in a range of 60 μm or more and 195 μm or less,more preferably in a range of 70 μm or more and 190 μm or less, evenmore preferably in a range of 80 μm or more and 185 μm or less. When thethickness of the first wavelength converting layer 51 is more than 200μm, and when using for a light emitting device, demands for thinning thelight emitting device may not be satisfied. When the thickness of thefirst wavelength converting layer 51 is less than 50 μm, the totalamount of the first fluorescent material 61 and the second fluorescentmaterial 62 contained in the first wavelength converting layer 51becomes small. Thus, the excitation light passes the wavelengthconverting member without being wavelength-converted by the fluorescentmaterials, resulting in that a desired color tone may not be provided.

The wavelength converting member according to an embodiment of thepresent disclosure may be a wavelength converting member comprising: asecond wavelength converting layer containing a first fluorescentmaterial having a light emission peak wavelength in a range of 620 nm ormore and 660 nm or less and a first resin; and a third wavelengthconverting layer containing a second fluorescent material having a lightemission peak wavelength in a range of 510 nm or more and 560 nm or lessand a second resin, wherein the average particle diameter, as measuredaccording to the Fisher Sub-Sieve Sizer method, of the first fluorescentmaterial is in a range of 2 μm or more and 30 μm or less, wherein thesecond fluorescent material comprises a β-SiAlON fluorescent material,the circularity of the β-SiAlON fluorescent material is 0.7 or more, andthe volume average particle diameter, as measured according to the laserdiffraction scattering particle size distribution measuring method, ofthe β-SiAlON fluorescent material is in a range of 2 μm or more and 30μm or less, and wherein the thickness of each of the second wavelengthconverting layer and the third wavelength converting layer is in a rangeof 10 μm or more and 150 μm or less.

FIG. 2 is a schematic cross-sectional view showing one example of awavelength converting member 50. As shown in FIG. 2, the wavelengthconverting member 50 contains a second wavelength converting layer 52and a third wavelength converting layer 53. The second wavelengthconverting layer 52 contains the first fluorescent material 61 and afirst resin 56, and substantially does not contain a second fluorescentmaterial. Here, the phrase “substantially does not contain a secondfluorescent material” refers to a state where almost no secondfluorescent material exists in the second wavelength converting layer52, and although it is not limited, the amount of the second fluorescentmaterial is 1% by mass or less relative to the total amount of thesecond wavelength converting layer 52. The third wavelength convertinglayer 53 contains the second fluorescent material 62 and a second resin57, and substantially does not contain a first fluorescent material.Here, the phrase “substantially does not contain a first fluorescentmaterial” refers to a state where almost no first fluorescent materialexists in the third wavelength converting layer 53, and although it isnot limited, the amount of the first fluorescent material is 1% by massor less relative to the total amount of the third wavelength convertinglayer 53. When the wavelength converting member 50 contains the secondwavelength converting layer 52 containing the first fluorescent material61 and the third wavelength converting layer 53 containing the secondfluorescent material 62, mixed-color light having a desired color tone,formed by converting the wavelength of the excitation light emitted fromthe light emitting element by the second wavelength converting layer 52and the third wavelength converting layer 53, can be provided. Further,since the type of the fluorescent materials contained in the secondwavelength converting layer 52 and the third wavelength converting layer53 is different, the laminating order of the second wavelengthconverting layer 52 and the third wavelength converting layer 53 can bechanged depending on the characteristics of the fluorescent materialcontained in the wavelength converting layer by considering anenvironmental atmosphere such as heat generated from the light emittingelement, humidity, or temperature, and a light emitting device capableof providing a desired color tone and suppressing deterioration of thefluorescent material can be obtained.

The thickness of each of the second wavelength converting layer 52 andthe third wavelength converting layer 53 is in a range of 10 μm or moreand 150 μm or less, and preferably in a range of 15 μm or more and 140μm or less, more preferably in a range of 20 μm or more and 130 μm orless, even more preferably in a range of 25 μm or more and 120 μm orless. When the thickness of each of the second wavelength convertinglayer 52 and the third wavelength converting layer 53 is more than 150μm, the thickness of layer formed by laminating the two wavelengthconverting layers becomes more than 200 μm, and when using for a lightemitting device, demands for thinning the light emitting device may notbe satisfied. When the thickness of each of the second wavelengthconverting layer 52 and the third wavelength converting layer 53 is lessthan 10 μm, the amount of each of the first fluorescent material 61contained in the second wavelength converting layer 52 and the secondfluorescent material 62 contained in the third wavelength convertinglayer 53 becomes small. Thus, the excitation light passes the wavelengthconverting member without being wavelength-converted by the firstfluorescent material or the second fluorescent material, or thewavelength of the excitation light is not sufficientlywavelength-converted by the first fluorescent material or the secondfluorescent material, resulting in that a desired color tone may not beprovided.

Second Fluorescent Material

The second fluorescent material having a light emission peak wavelengthin a range of 510 nm or more and 560 nm or less contains a β-SiAlONfluorescent material, the circularity of the β-SiAlON fluorescentmaterial is 0.7 or more, and the volume average particle diameter, asmeasured according to the laser diffraction scattering particle sizedistribution measuring method, of the β-SiAlON fluorescent material isin a range of 2 μm or more and 30 μm or less.

β-SiAlON Fluorescent Material

The β-SiAlON fluorescent material is a solid solution in which a part ofsilicon and nitride each contained in silicon nitride is replaced withaluminum and oxygen. The β-SiAlON fluorescent material belongs to ahexagonal crystal system, and has a crystal structure in which layersformed of a tetrahedral framework of Al(O, N)₄ are laminated in thec-axis direction. Since the β-SiAlON fluorescent material has ahexagonal crystal structure, the particles of the β-SiAlON fluorescentmaterial tend to largely contain particles having an anisotropic shapesuch as a needle shape, a columnar shape, a cylindrical shape, a plateshape, or a sheet shape. When the particle shape of the β-SiAlONfluorescent material is an anisotropic shape, and when constituting alight emitting device, the arrangement state of the β-SiAlON fluorescentmaterial with respect to the light emitting element varies for eachfluorescent material, and the locations where the anisotropic-shapedfluorescent material is irradiated with light emitted from the lightemitting element are different. Accordingly, the color tones may bedifferent for each fluorescent material and even for each light emittingdevice. In particular, when the β-SiAlON fluorescent material iscontained in a relatively thin sheet-shaped wavelength converting memberand the sheet-shaped wavelength converting member is arranged in frontof the light emitting element, almost all of the light emitted from thelight emitting element is entered into the sheet-shaped wavelengthconverting member in a vertical direction, and the distance reaching thefluorescent material contained in the sheet-shaped wavelength convertingmember becomes short. Thus, the anisotropic-shaped fluorescent materialis easy to be uniformly irradiated with the light emitted from the lightemitting element. When the β-SiAlON fluorescent material is arranged invarious states such as a horizontal state, a vertical state, and anoblique state with respect to the incident direction of the light, thelight emitted from the light emitting element is entered from varioussurface directions of the β-SiAlON fluorescent material, the degree ofwavelength conversion by the fluorescent material varies depending onthe locations where the particles of the fluorescent material areirradiated with the light, and the color tone tends to largely vary foreach wavelength converting member.

The wavelength converting member contains the β-SiAlON fluorescentmaterial as a second fluorescent material contained in the sheet-shapedwavelength converting member. When the circularity of the β-SiAlONfluorescent material is 0.7 or more and the volume average particlediameter thereof, as measured according to the laser diffractionscattering particle size distribution measuring method, is in a range of2 μm or more and 30 μm or less, the change in chromaticity caused by thedeviation of location where the fluorescent material is irradiated withthe light emitted from the light emitting element is suppressed, so thatthe color tone deviation for each light emitting device can besuppressed.

The circularity of the β-SiAlON fluorescent material is 0.7 or more. Itindicates that the closer the circularity is 1.0, the more similar theshape is a circular shape. The circularity can be determined by:randomly selecting a particle from the photographed image by theobservation using a scanning electron microscope (SEM), a transmissionelectron microscope (TEM), or an optical microscope; measuring aprojected area (S (m²)) and a peripheral length (L (m)) of the particleusing an image processing software or the like; and calculatingaccording to the following formula (1). The circularity can bedetermined as an average value of the group having an arbitrary numberof particles, and is preferably determined as an average value of 100 ormore particles. In the present specification, the circularity refers toan average value of the circularities of 5,000 β-SiAlON fluorescentmaterial particles that are randomly selected.Circularity=4πS/L²  (1)

The circularity of the β-SiAlON fluorescent material that is used forthe wavelength converting member is 0.7 or more, and preferably 0.71 ormore, more preferably 0.72 or more, even more preferably 0.74 or more,still more preferably 0.75 or more, particularly preferably 0.80 or moreand 1.0 or less. When the circularity of the β-SiAlON fluorescentmaterial contained in the wavelength converting member is 0.7 or more,and when containing the nearly circular β-SiAlON fluorescent material,the light emitted from the light emitting element is entered from asubstantially uniform surface direction with respect to the β-SiAlONfluorescent material, and the change in chromaticity caused by enteringthe excitation light from various surface directions is suppressed, sothat a wavelength converting member capable of providing a desired colortone can be obtained. Further, when the circularity is 0.7 or more, theβ-SiAlON fluorescent material contained in the wavelength convertingmember is easy to be uniformly dispersed in the resin. In the case ofproducing a light emitting device, when the wavelength converting membercontaining the fluorescent material having an anisotropic shape such asa cylindrical shape or a plate shape is cut into a sheet shape, arelatively hard fluorescent material is hardly cut, and thus thefluorescent material may stick out to the outside from the end surfaceof the cut wavelength converting member. Also, when cutting a relativelyhard fluorescent material, strain may be generated on the sheet-shapedwavelength converting member. When the circularity of the β-SiAlONfluorescent material contained in the wavelength converting member is0.7 or more, inconvenient behaviors in the production, such as stickingout of the fluorescent material to the outside from the end surface ofthe cut wavelength converting member and strain generated on thewavelength converting member, can be improved.

The volume average particle diameter (hereinafter also referred to as“volume average particle diameter Dm2”), as measured according to thelaser diffraction scattering particle size distribution measuringmethod, of the β-SiAlON fluorescent material is in a range of 2 μm ormore and 30 μm or less, and preferably in a range of 3 μm or more and 28μm or less, more preferably in a range of 5 μm or more and 25 μm orless, even more preferably in a range of 6 μm or more and 20 μm or less.When the volume average particle diameter of the β-SiAlON fluorescentmaterial is more than 30 μm, and when the β-SiAlON fluorescent materialis contained in the sheet-shaped wavelength converting member, it may behard to thin the thickness of the sheet due to too large volume averageparticle diameter. Further, when the volume average particle diameter ofthe β-SiAlON fluorescent material is more than 30 μm, it is hard for thefluorescent material to be uniformly arranged to the surface of thesheet-shaped wavelength converting member, and the light emitted fromthe light emitting element is not irradiated on the fluorescent materialto thereby pass through the wavelength converting member. Thus, thechromaticity is changed, and a desired color tone may not be obtained.When the volume average particle diameter of the β-SiAlON fluorescentmaterial is less than 2 μm, the light emitted from the light emittingelement may not be efficiently wavelength-converted.

The aspect ratio of the β-SiAlON fluorescent material is preferably 0.62or more, and the ratio (D2/Dm2) (hereinafter also referred to as“particle diameter ratio D2/Dm2”) of the average particle diameter(hereinafter also referred to as “average particle diameter D2”), asmeasured according to the FSSS method, to the volume average particlediameter Dm2, as measured according to the laser diffraction scatteringparticle size distribution measuring method, is preferably 0.67 or more.The aspect ratio of the β-SiAlON fluorescent material is more preferably0.64 or more, even more preferably 0.66 or more, still more preferably0.68 or more. The aspect ratio of the β-SiAlON fluorescent material isgenerally 1.0 or less. It indicates that the smaller the value of theaspect ratio is, the more similar the shape is an anisotropic shape suchas a cylindrical shape or a plate shape, and the closer the aspect ratiois 1, the more similar the shape is an isotropic shape such as acircular shape or a polygonal shape. When the aspect ratio of theβ-SiAlON fluorescent material is 0.62 or more, and when the SiAlONfluorescent material having a shape similar to an isotropic shape iscontained in the wavelength converting member, the light emitted fromthe light emitting element is entered from a substantially uniformsurface direction with respect to the β-SiAlON fluorescent material, andthe change in chromaticity caused by entering the excitation light fromvarious surface directions is suppressed, so that a wavelengthconverting member capable of providing a desired color tone can beobtained. Further, when the aspect ratio is 0.62 or more, the β-SiAlONfluorescent material contained in the wavelength converting member iseasy to be uniformly dispersed in the resin. In the case of producing alight emitting device, when the aspect ratio of the β-SiAlON fluorescentmaterial contained in the wavelength converting member is 0.62 or moreand the β-SiAlON fluorescent material has a shape similar to anisotropic shape, inconvenient behaviors in the production, such assticking out of the fluorescent material to the outside from the endsurface of the cut wavelength converting member and strain generated onthe wavelength converting member, can be improved. The aspect ratio ofthe β-SiAlON fluorescent material can be determined by: randomlyselecting a particle from the photographed image by the observationusing a scanning electron microscope (SEM), a transmission electronmicroscope (TEM), or an optical microscope; measuring a long diameterand a short diameter of the particle; and calculating a ratio (shortdiameter/long diameter) of the short diameter to the long diameter asthe aspect ratio. The aspect ratio is preferably determined as anaverage value of 100 or more particles. In the present specification,the aspect ratio refers to an average value of the aspect ratios of5,000 β-SiAlON fluorescent material particles that are randomlyselected.

The particle diameter ratio D2/Dm2, which is the ratio of the averageparticle diameter D2, as measured according to the FSSS method, to thevolume average particle diameter Dm2, as measured according to the laserdiffraction scattering particle size distribution measuring method, ofthe β-SiAlON fluorescent material is preferably 0.67 or more. Theparticle diameter ratio D2/Dm2 of the β-SiAlON fluorescent material ismore preferably 0.68 or more, even more preferably 0.70 or more, stillmore preferably 0.72 or more, particularly preferably 0.75 or more, andgenerally 1.0 or less. The particle diameter ratio D2/Dm2 indicates aratio of the average particle diameter D2 of primary particles to theaverage particle diameter D2 of particles as measured irrespective ofprimary particles and secondary particles, and when the value of theparticle diameter ratio D2/Dm2 is closer to 1, the ratio of the primaryparticles present in the particles is larger. When the aspect ratio ofthe β-SiAlON fluorescent material contained in the wavelength convertingmember is 0.62 or more and the particle diameter ratio D2/Dm2 thereof is0.67 or more, and when the β-SiAlON fluorescent material as primaryparticles having a shape similar to an isotropic shape is contained inthe wavelength converting member, the β-SiAlON fluorescent material iswell dispersed in the resin, the β-SiAlON fluorescent material isuniformly arranged in the wavelength converting member, the lightemitted from the light emitting element is entered from a substantiallyuniform surface direction with respect to the β-SiAlON fluorescentmaterial, and the change in chromaticity caused by entering theexcitation light from various surface directions is suppressed, so thata wavelength converting member capable of providing a desired color tonecan be obtained. In the case of producing a light emitting device, whenthe β-SiAlON fluorescent material contained in the wavelength convertingmember has a shape similar to an isotropic shape and is uniformlydispersed in the resin to be arranged therein, inconvenient behaviors inthe production, such as sticking out of the fluorescent material to theoutside from the end surface of the cut wavelength converting member andstrain generated on the wavelength converting member, can be improved.

The β-SiAlON fluorescent material preferably contains a compositionrepresented by the following formula (I).Si_(6-z)Al_(z)O_(z)N_(8-z):Eu  (I)

wherein z satisfies 0<z≤4.2, and wherein the part before the column (:)in the formula representing the composition of the fluorescent materialexpresses elements constituting of a host crystal and a molar ratio theelements, and the part after the column (:) expresses an activatingelement (the same applies to the following formulae that represent acomposition of the fluorescent material). The term ‘molar ratio’ refersto the molar amount of an element in one mole of the chemicalcomposition of the fluorescent material.

As for the β-SiAlON fluorescent material, by adjusting the heattreatment temperature and the heat treatment atmosphere of theheat-treated product obtained by subjecting the mixture, in which theraw materials constituting the β-SiAlON fluorescent material are mixed,to the heat treatment, and adjusting the grinding conditions of theresultant heat-treated product, a β-SiAlON fluorescent material having adesired circularity and volume average particle diameter Dm2 can beproduced. For example, a β-SiAlON fluorescent material having acircularity of 0.7 or more and a volume average particle diameter Dm2 ina range of 2 μm or more and 30 μm or less can be produced according tothe method described in Japanese Patent Application No. 2017-97125.Also, a β-SiAlON fluorescent material, in which the aspect ratio is 0.62or more and the particle diameter ratio D2/Dm2 of the average particlediameter D2 to the volume average particle diameter Dm2 is 0.67 or more,can be produced according to the aforementioned method.

The second fluorescent material may contain other fluorescent materialthan the β-SiAlON fluorescent material as long as a desired color tonecan be obtained. When the second fluorescent material contains otherfluorescent material than the β-SiAlON fluorescent material, the otherfluorescent material serving as the second fluorescent material is alsoa fluorescent material having a light emission peak wavelength in arange of 510 nm or more and 560 nm or less. It is preferable that thesecond fluorescent material further comprises, for example, achlorosilicate-based fluorescent material, a Mn²⁺-activated aluminatefluorescent material having a composition containing at least onealkaline earth metal element selected from the group consisting of Ba,Sr, and Ca, and at least one fluorescent material selected from thegroup consisting of γ-AlON fluorescent materials. The volume averageparticle diameter, as measured according to the laser diffractionscattering particle size distribution measuring method, of the otherfluorescent material than the β-SiAlON fluorescent material that iscontained in the second fluorescent material is preferably in a range of2 μm or more and 30 μm or less. When the volume average particlediameter of the other fluorescent material than the β-SiAlON fluorescentmaterial that is contained in the second fluorescent material fallswithin the aforementioned range, the thickness of the sheet-shapedwavelength converting member can be thinned, and even in the case ofthinning the thickness, the change in chromaticity is suppressed byuniformly arranging the second fluorescent material in the sheet-shapedwavelength converting member, so that a wavelength converting membercapable of providing a desired color tone can be obtained.

The chlorosilicate fluorescent material preferably contains acomposition represented by the following formula (II).M¹ ₈MgSi₄O₁₆X¹ ₂:Eu  (II)

wherein M¹ represents at least one selected from the group consisting ofCa, Sr, Ba, and Zn, and X¹ represents at least one selected from thegroup consisting of F, Cl, Br, and I.

The Mn²⁺-activated aluminate fluorescent material having a compositioncontaining at least one alkaline earth metal element selected from thegroup consisting of Ba, Sr, and Ca preferably contains a compositionrepresented by the following formula (III).M² _(a)Mg_(b)Mn_(c)Al_(d)O_(a+b+c+1.5d)  (III)

wherein M² represents at least one alkaline earth metal element selectedfrom the group consisting of Ba, Sr, and Ca, and a, b, c, and d eachsatisfy 0.5≤a≤1.0, 0≤b<0.4, 0.3≤c≤0.7, 8.5≤d≤13.0, and 9.0≤b+c+d≤14.0.

The γ-AlON fluorescent material is a Mn²⁺-activated aluminum oxynitridefluorescent material containing a spinel-type aluminum oxynitridecrystal (γ-AlON) that belongs to a cubic crystal system. The γ-AlONfluorescent material preferably contains a composition represented bythe following formula (IV).Mn_(e)Mg_(f)Li_(g)Al_(h)O_(i)N_(j)  (IV)

wherein e, f, g, h, i, and j each satisfy 0.005≤e≤0.02, 0.01≤f≤0.035,0.01≤g≤0.04, 0.3≤h≤0.45, 0.4≤i≤0.6, 0.3≤j≤0.6, when e+f+g+h+i+j=1.

It is preferable that the second fluorescent material further contains afluorescent material containing any of the compositions represented bythe formulae (II) to (IV).

First Fluorescent Material

The first fluorescent material having a light emission peak wavelengthin a range of 620 nm or more and 660 nm or less has an average particlediameter (hereinafter also referred to as “average particle diameterD1”), as measured according to the FSSS method, in a range of 2 μm ormore and 30 μm or less. The average particle diameter D1, as measuredaccording to the FSSS method, of the first fluorescent material ispreferably in a range of 3 μm or more and 28 μm or less, more preferablyin a range of 5 μm or more and 25 μm or less, even more preferably in arange of 7 μm or more and 22 μm or less, still more preferably in arange of 8 μm or more and 20 μm or less. When the average particlediameter D1 of the first fluorescent material is more than 30 μm, thesheet-shaped wavelength converting member cannot be thinned, and thedemands for thinning may not be satisfied. Further, when the averageparticle diameter D1 of the first fluorescent material is more than 30μm, it is hard for the first fluorescent material to be uniformlyarranged to the surface of the sheet-shaped wavelength convertingmember, and the light emitted from the light emitting element is notirradiated on the first fluorescent material to thereby pass through thewavelength converting member. Thus, a desired color tone cannot beobtained, and color unevenness may occur. When the average particlediameter D1, as measured according to the FSSS method, of the firstfluorescent material is less than 2 μm, the light emitted from the lightemitting element may not be efficiently wavelength-converted. The firstfluorescent material having an average particle diameter D1 in a rangeof 2 μm or more and 30 μm or less can be produced by performingtreatments such as a crushing treatment, a grinding treatment, and aclassification treatment, and adjusting the conditions of the respectivetreatments.

The kind of the first fluorescent material having a light emission peakwavelength in a range of 620 nm or more and 660 nm or less is notparticularly limited as long as a desired color tone can be obtained.The first fluorescent material having a light emission peak wavelengthin a range of 620 nm or more and 660 nm or less preferably comprises: aMn⁴⁺-activated fluoride fluorescent material; a fluorescent materialcontaining an Eu²⁺-activated silicon nitride having a compositioncontaining at least one element selected from Sr and Ca, and Al; and atleast one fluorescent material selected from the group consisting offluorescent materials containing an Eu²⁺-activated aluminum nitridehaving a composition containing at least one element selected from thegroup consisting of alkaline earth metal elements and at least oneelement selected from the group consisting of alkali metal elements.

The Mn⁴⁺-activated fluoride fluorescent material preferably contains acomposition represented by the following formula (i).A₂[M³ _(1-k)Mn⁴⁺ _(k)F₆]  (i)

wherein A represents at least one selected from the group consisting ofK, Li, Na, Rb, Cs, and NH₄ ₊ , M³ represents at least one elementselected from the group consisting of group 4 elements and group 14elements, and k satisfies 0<k<0.2.

The fluorescent material containing an Eu²⁺-activated silicon nitridehaving a composition containing at least one element selected from Srand Ca, and Al preferably contains a composition represented by thefollowing formula (ii). However, the fluorescent material containing thecomposition represented by the following formula (ii) may be indicatedas a CaAlSiN₃:Eu fluorescent material or a (Sr,Ca)AlSiN₃:Eu fluorescentmaterial.(Ca_(1-m-n)Sr_(m)Eu_(n))_(p)Al_(q)Si_(r)N_(s)  (ii)

wherein m, n, p, q, r, and s each satisfy 0≤m≤1, 0<n<1.0, 0<m+n<1.0,0.8≤p≤1.0, 0.8≤q≤1.2, 0.8≤r≤1.2, 1.9≤q+r≤2.1, and 2.5≤s≤3.5respectively,

wherein a value of m times p represents a molar ratio of Sr in thecomposition represented by the formula (ii), and preferably satisfies0≤m≤0.98, more preferably 0≤m≤0.95, even more preferably 0≤m≤0.9, and

wherein a value of n times p represents a molar ratio of the activatingelement Eu in the composition represented by the formula (ii), andpreferably satisfies 0.0001≤n≤0.2, more preferably 0.0001≤n≤0.1, evenmore preferably 0.0002≤n≤0.05.

The fluorescent material containing an Eu²⁺-activated aluminum nitridehaving a composition containing at least one element selected from thegroup consisting of alkaline earth metal elements and at least oneelement selected from the group consisting of alkali metal elementspreferably contains a composition represented by the following formula(iii).M⁵ _(t)M⁶ _(u)M⁷ _(v)Al_(3-w)Si_(w)N_(x)  (iii)

wherein M⁵ represents at least one element selected from the groupconsisting of Ca, Sr, Ba and Mg, M⁶ represents at least one elementselected from the group consisting of Li, Na, and K, M⁷ represents atleast one element selected from the group consisting of Eu, Ce, Tb andMn, and t, u, v, w and x each satisfy 0.80≤t≤1.05, 0.80≤u≤1.05,0.001<v≤0.1, 0≤w≤0.5, and 3.0≤x≤5.0.

The first fluorescent material preferably contains a fluorescentmaterial containing any of the compositions represented by the formulae(i) to (iii).

Resin

Examples of the resin contained in the wavelength converting member mayinclude a silicone resin, an epoxy resin, a phenol resin, apolycarbonate resin, an acrylic resin, and a modified resin of any ofthese. Among others, a silicone resin or an epoxy resin having excellentheat resistance is preferred, and a silicone resin having excellent heatresistance and light resistance is more preferred. Examples of thesilicone resin may include a dimethyl silicone resin, a phenylmethylsilicone resin, and a diphenyl silicone resin. Hereinafter, the“modified resin” in the present specification shall contain a hybridresin.

The mass ratio of the resin to the total of the first fluorescentmaterial and the second fluorescent material in the first wavelengthconverting layer is not particularly limited as long as a desired colortone can be obtained by the wavelength converting member and an effectof improving the production yield can be obtained. The mass ratio(resin:total of first fluorescent material and second fluorescentmaterial) of the resin to the total of the first fluorescent materialand the second fluorescent material in the first wavelength convertinglayer is preferably in a range of 100:50 to 100:260, more preferably ina range of 100:55 to 100:255, even more preferably in a range of 100:60to 100:250, still more preferably in a range of 100:65 to 100:245. Whenthe mass ratio (resin total of first fluorescent material and secondfluorescent material) of the resin to the total of the first fluorescentmaterial and the second fluorescent material in the first wavelengthconverting layer falls within the aforementioned range, a desired colortone can be obtained, and a first wavelength converting layer having adesired thickness can be produced. The mass ratio (first fluorescentmaterial second fluorescent material) of the first fluorescent materialto the second fluorescent material in the first wavelength convertinglayer is changed depending on a desired color tone, but is preferably ina range of 100:10 to 100:70, more preferably in a range of 100:15 to100:65, even more preferably in a range of 100:20 to 100:60.

As for the first wavelength converting layer, the arrangement relationof the first fluorescent material or the second fluorescent material inthe first wavelength converting layer is not particularly limited aslong as a desired color tone can be obtained and an effect of improvingthe production yield can be obtained. For example, the first wavelengthconverting layer may be formed by arranging the first fluorescentmaterial and the second fluorescent material so as to be mixed with eachother in the thickness direction of the first wavelength convertinglayer. Further, the first wavelength converting layer may be formed asfollows: in the first wavelength converting layer, for example, thesecond fluorescent material is previously added to a liquid resin; thepreviously-added second fluorescent material is precipitated so as to bearranged eccentrically to one surface side in a process of curing theresin; then, the first fluorescent material is added and arranged on thesecond fluorescent material in the thickness direction; and the resin iscured. As for the order of adding the fluorescent materials to the resinfor forming the first wavelength converting layer, it does not matterwhether the first fluorescent material is first or the secondfluorescent material is first. In order to precipitate the fluorescentmaterial, the fluorescent material may be naturally precipitated, or maybe forcibly precipitated using a centrifugal separator. The firstwavelength converting layer has a first main surface as one of thesurfaces and a second main surface that is a surface on a side oppositeto the first main surface, and may be formed as follows: one of thefirst fluorescent material or the second fluorescent material iseccentrically arranged on the first main surface side, and another oneof the first fluorescent material or the second fluorescent material iseccentrically arranged on the second main surface side, so as to have anarea where the first fluorescent material and the second fluorescentmaterial are mixedly present in the thickness direction of the firstwavelength converting layer.

The mass ratio of the resin to the first fluorescent material in thesecond wavelength converting layer is not particularly limited as longas a desired color tone can be obtained by the wavelength convertingmember. The mass ratio (resin:first fluorescent material) of the resinto the first fluorescent material in the second wavelength convertinglayer is preferably in a range of 100:50 to 100:260, more preferably ina range of 100:55 to 100:255, even more preferably in a range of 100:60to 100:250, still more preferably in a range of 100:65 to 100:245. Whenthe mass ratio (resin:first fluorescent material) of the resin to thefirst fluorescent material in the second wavelength converting layerfalls within the aforementioned range, and when using by laminating thethird wavelength converting layer, a desired color tone can be obtained,and a second wavelength converting layer having a desired thickness canbe produced.

The mass ratio of the resin to the second fluorescent material in thethird wavelength converting layer is not particularly limited as long asa desired color tone can be obtained by the wavelength converting memberand an effect of improving the production yield can be obtained. Themass ratio (resin:second fluorescent material) of the resin to thesecond fluorescent material in the third wavelength converting layer ispreferably in a range of 100:50 to 100:150, more preferably in a rangeof 100:55 to 100:145, even more preferably in a range of 100:60 to100:140, still more preferably in a range of 100:65 to 100:135. When themass ratio (resin:second fluorescent material) of the resin to thesecond fluorescent material in the third wavelength converting layerfalls within the aforementioned range, and when using by laminating thesecond wavelength converting layer, a desired color tone can beobtained, and a third wavelength converting layer having a desiredthickness can be produced.

The second wavelength converting layer containing the resin and thefirst fluorescent material and the third wavelength converting layercontaining the resin and the second fluorescent material may beindividually produced in a sheet shape, and the second wavelengthconverting layer and the third wavelength converting layer may be bondedtogether to produce one wavelength converting member.

The first wavelength converting layer, the second wavelength convertinglayer, and the third wavelength converting layer have translucency tothe light emitted from the light emitting element and the light that iswavelength-converted by the first fluorescent material and the secondfluorescent material. Hereinafter, the first wavelength converting layercontaining the first fluorescent material and the second fluorescentmaterial, the second wavelength converting layer containing the firstfluorescent material, and the third wavelength converting layercontaining the second fluorescent material may be referred to as just“wavelength converting layer”. Here, the “translucency” means a statewhere the light transmittance in the light emission peak wavelength ofthe light emitting element is preferably 60% or more, more preferably70% or more, even more preferably 80% or more.

Translucent Layer

The wavelength converting member preferably comprises a translucentlayer containing no fluorescent material. The translucent layer ispreferably arranged at a position closer to the external environmentthan the wavelength converting layer. FIG. 3 is a diagram showing aschematic cross-section of the wavelength converting member 50 in whichthe translucent layer 55 is arranged at a position closer to theexternal environment than the first wavelength converting layer 51. Whenthe wavelength converting member 50 comprises the translucent layer 55containing no fluorescent material at a position closer to the externalenvironment than the first wavelength converting layer 51, the firstfluorescent material 61 and the second fluorescent material 62 eachcontained in the first wavelength converting member 51 are protectedfrom the external environments such as temperature and humidity, andthus deterioration of the fluorescent material can be suppressed.Examples of the resin constituting the translucent layer may include aresin similar to the resin contained in the first wavelength convertinglayer, the second wavelength converting layer, or the third wavelengthconverting layer (hereinafter also referred to as “wavelength convertinglayer”). The resin constituting the translucent layer may be the samekind as the resin constituting the wavelength converting layer, or maybe a different kind therefrom. When the resin constituting thetranslucent layer is the same kind as the resin constituting thewavelength converting layer, the translucent layer and the wavelengthconverting layer can be bonded together while improving the adhesivenessbetween the layers. When the resin constituting the translucent layer isa different kind from the resin constituting the wavelength convertinglayer, a wavelength converting member formed by adjusting a refractiveindex of the emitted light can be obtained.

The translucent layer can be produced in a sheet shape in addition tothe wavelength converting layer. As for the wavelength convertingmember, the wavelength converting layer and the translucent layer, whichare individually produced in a sheet shape, may be bonded together toproduce one wavelength converting member. Further, as for thetranslucent layer, the first fluorescent material and/or the secondfluorescent material added to the liquid resin is previouslyprecipitated at the time of forming a wavelength converting layer, and atranslucent layer containing no first fluorescent material and secondfluorescent material may be formed at a side opposite to the side wherethe first fluorescent material and/or the second fluorescent material isprecipitated in a thickness direction.

FIG. 4 is a diagram showing a schematic cross-section of the wavelengthconverting member 50 in which the third wavelength converting layer 53,the second wavelength converting layer 52, and the translucent layer 55are laminated in this order. When the second wavelength converting layercontains a Mn⁴⁺-activated fluoride fluorescent material, as shown inFIG. 4, the second wavelength converting layer 52 is preferably arrangedbetween the translucent layer 55 and the third wavelength convertinglayer 53 in the wavelength converting member 50. When the Mn⁴⁺-activatedfluoride fluorescent material is used as a first fluorescent material,the fluoride fluorescent material is easily deteriorated due to aninfluence of moisture or heat. As shown in FIG. 4, when the secondwavelength converting layer 52 containing a fluoride fluorescentmaterial is arranged between the translucent layer 55 and the thirdwavelength converting layer 53, the fluoride fluorescent material thatis the first fluorescent material 61 contained in the second wavelengthconverting layer 52 is protected from the external environments such ashumidity and temperature by the translucent layer 55, and also protectedfrom the heat generated from the light emitting element by the thirdwavelength converting layer 53.

The thickness of the translucent layer is not particularly limited. Thethickness of the translucent layer is preferably in a range of 5 μm ormore and 100 μm or less, more preferably in a range of 5 μm or more and90 μm or less, even more preferably in a range of 5 μm or more and 80 μmor less, still more preferably in a range of 5 μm or more and 70 μm orless. When the thickness of the translucent layer falls within a rangeof 5 μm or more and 100 μm or less, and when using for a light emittingdevice, demands for thinning the light emitting device can be satisfied,and the fluorescent material can be sufficiently protected from theexternal environments such as humidity and temperature.

Filler

At least one of the first wavelength converting layer, the secondwavelength converting layer, the third wavelength converting layer, andthe translucent layer preferably contains a filler. The filler ispreferably at least one selected from the group consisting of siliconoxide, zirconium oxide, titanium oxide, zinc oxide, and aluminum oxide.By containing the filler in the wavelength converting layer and/or thetranslucent layer, scattering of the light emitted from the lightemitting element or the light that is wavelength-converted by thefluorescent material is increased, so that a desired color tone can beeasily obtained. For example, by using a nanop article as the filler,scattering including Rayleigh scattering of the light emitted from thelight emitting element is increased, so that the amount of usedfluorescent material can be also reduced. The nanop article refers to aparticle having a volume average particle diameter in a range of 1 nm ormore and 100 nm or less. The volume average particle diameter of thenanoparticle refers to a volume particle diameter (median diameter: Dm)where the volume cumulative frequency from the small diameter sidereaches 50% in the volume-based particle size distribution, as measuredaccording to the laser diffraction scattering particle size distributionmeasuring method.

The amount of the filler contained in the wavelength converting layerand/or the translucent layer is not particularly limited as long as thelight-scattering effect can be improved without hindering the effect ofthe present invention. The mass ratio (resin:filler) of the resin to thefiller contained in the wavelength converting layer and/or thetranslucent layer is, from the viewpoint of improving thelight-scattering effect, preferably in a range of 100:0.1 to 100:40,more preferably in a range of 100:0.1 to 100:30, even more preferably ina range of 100:0.1 to 100:20, still more preferably in a range of100:0.1 to 100:10.

Light Emitting Device

The light emitting device comprises the wavelength converting member anda light emitting element having a light emission peak wavelength in arange of 400 nm or more and 480 nm or less. FIG. 5 is a schematicperspective view of a light emitting device 100. FIG. 6 is a schematiccross-sectional view of the light emitting device 100.

The light emitting device 100 as shown in FIG. 5 is a side surfaceemission-type (also referred to as “side view-type”) and can be alsoused as a top surface emission-type (also referred to as “topview-type”). In the side surface emission-type light emitting device,the mounting direction and the main light emission direction areperpendicular to each other. In the top surface emission-type lightemitting device, the mounting direction and the main light emissiondirection are parallel to each other. The front view shape of the lightemitting device, that is, the shape viewed from the main light emissiondirection can be appropriately selected, and is preferably a rectangularshape from the viewpoint of mass productivity. When the light emittingdevice is a side surface emission-type, the front view shape ispreferably a rectangular shape having long and short side directions.When the light emitting device is a top surface emission-type, the frontview shape is preferably a square shape. Also, the light emittingelement and the wavelength converting member preferably have a frontview shape similar to that of the light emitting device. The lightemitting device may be a chip size package (CSP) type containing nowiring board and instead, having positive and negative electrodes of thelight emitting element or bump electrodes connected to the positive andnegative electrodes as terminals for external connection.

As shown in FIG. 5 and FIG. 6, the light emitting device 100 comprises achip substrate 101, a conductive adhesive member 20, a light emittingelement 30, a light guide member 40, a wavelength converting member 50,and a light reflective covering member 701. The chip substrate 101 has awiring 111 and a base body 151 that holds the wiring 111. The lightemitting element 30 is flip-chip mounted on the wiring 111 of the chipsubstrate via the conductive adhesive member 20. The wavelengthconverting member 50 contains: a first wavelength converting layer 51containing a first fluorescent material 61, a second fluorescentmaterial 62, and a resin; and a translucent layer 55 containing nofluorescent material. The wavelength converting member 50 has a sizeenough to entirely cover the light emitting element 30 in the frontview. The wavelength converting member 50 is bonded to the lightemitting element 30 via the light guide member 40. The covering member701 is formed by containing a white pigment 77 in a resin 75. Thecovering member 701 is formed on the chip substrate 101, and covers sidesurfaces of each of the light emitting element 30, the light guidemember 40, and the wavelength converting member 50. The covering member701 surrounds whole side circumference of the light emitting element 30and the wavelength converting member 50. The front surface of thewavelength converting member 50 and the front surface of the coveringmember 701 constitute substantially the same surface. The wavelengthconverting member 50 has a first main surface 51 a that is one surfaceof the first wavelength converting layer 51 and a second main surface 55b that is one surface of the translucent layer 55 on a side opposite tothe first main surface. The first main surface 51 a of the wavelengthconverting member 50 is bonded to one surface of the light emittingelement 30 via the light guide member 40.

FIG. 7 shows another example of the light emitting device. Thewavelength converting member 50 contains a second wavelength convertinglayer 52 containing a first fluorescent material 61, a third wavelengthconverting layer 53 containing a second fluorescent material 62, and atranslucent layer 55. The other members than the wavelength convertingmember 50 of the light emitting device 100 are the same as those of thelight emitting device 100 shown in FIG. 6. The wavelength convertingmember 50 has a first main surface 53 a that is one surface of the thirdwavelength converting layer 53 and a second main surface 55 b that isone surface of the translucent layer 55 on a side opposite to the firstmain surface. The first main surface 53 a that is one surface of thethird wavelength converting layer 53 of the wavelength converting member50 is bonded to one surface of the light emitting element 30 via thelight guide member 40. In the wavelength converting member 50, thesecond wavelength converting layer 52 is arranged between the thirdwavelength converting layer 53 and the translucent layer 55. When thesecond wavelength converting layer 52 contains a Mn⁴⁺-activated fluoridefluorescent material as the first fluorescent material 61, the fluoridefluorescent material that is the first fluorescent material 61 containedin the second wavelength converting layer 52 is protected from theexternal environments such as humidity and temperature by thetranslucent layer 55, and also protected from the heat generated fromthe light emitting element by the third wavelength converting layer 53.

Light Emitting Element

The light emitting element comprises at least a semiconductor elementstructure, and further comprises a substrate in most cases. Examples ofthe light emitting element may include an LED chip. The front view shapeof the light emitting element is preferably a rectangular shape andparticularly a square shape or a long rectangular shape in onedirection, and may also be other shapes. Even when the shape is, forexample, a hexagonal shape, the light emission efficiency can also beenhanced. The side surfaces of the light emitting element or thesubstrate may be vertical to the top surface, or may be inclinedinwardly or outwardly. The light emitting element preferably haspositive and negative (p, n) electrodes on the same surface. The numberof the light emitting element to be mounted on one light emitting devicemay be one, or may be a plural number. A plurality of light emittingelements can be electrically connected in series or in parallel. It ispreferable that the semiconductor element structure contains a laminateof semiconductor layers, that is, at least an n-type semiconductor layerand a p-type semiconductor layer, and an active layer is interposedtherebetween. The semiconductor element structure may contain positiveand negative electrodes and/or an insulating film. The positive andnegative electrodes can be constituted of gold, silver, tin, platinum,rhodium, titanium, aluminum, tungsten, palladium, nickel, or an alloy ofany of these. The insulating film can be constituted of an oxide or anitride of at least one element selected from the group consisting ofsilicon, titanium, zirconium, niobium, tantalum, and aluminum.

In the light emitting element, the light emission peak wavelength of thelight emitting element can be adjusted within a range of ultravioletregion to infrared region depending on the semiconductor material or themixed crystal ratio. As for the semiconductor material, it is preferableto use a nitride semiconductor capable of emitting short-wavelengthlight that can efficiently excite a fluorescent material. The nitridesemiconductor can be mainly represented by a general formula:In_(x)Al_(y)Ga_(1-x-y)N (where x≥0, y≥0, and x+y≤1). From the viewpointsof the light emission efficiency as well as the mixed color relationbetween the excitation of fluorescent material and the light emission,and the like, the light emission peak wavelength of the light emittingelement is in a range of 400 nm or more and 530 nm or less, andpreferably in a range of 400 nm or more and 500 nm or less, morepreferably in a range of 400 nm or more and 480 nm or less, even morepreferably in a range of 420 nm or more and 475 nm or less. In addition,an InAlGaAs-based semiconductor, an InAlGaP-based semiconductor, zincsulfide, zinc selenide, silicon carbide can be also used. The substrateof the light emitting element is a substrate for crystal growth capableof growing a crystal of the semiconductor mainly constituting thesemiconductor element structure, and may be a substrate for bondingcapable of bonding to the semiconductor element structure that isseparated from the substrate for crystal growth. When the substrate hastranslucency, a flip-chip mounting can be easily employed, and the lightextraction efficiency can be easily enhanced. Examples of the matrix ofthe substrate may include sapphire, spinel, gallium nitride, aluminumnitride, silicon, silicon carbide, gallium arsenide, gallium phosphide,indium phosphide, zinc sulfide, zinc oxide, zinc selenide, diamond, andthe like. Among others, sapphire is preferred. The thickness of thesubstrate is, for example, in a range of 0.02 mm or more and 1 mm orless, and preferably in a range of 0.05 mm or more and 0.3 mm or lessfrom the viewpoints of the strength of the substrate and the thicknessof the light emitting device.

Chip Substrate

The substrate is constituted of at least a wiring and a base body thatholds the wiring. In addition, the substrate may contain an insulatingprotective film such as a solder resist or a cover lay. The same appliesto the chip substrate 101.

Wiring

The wiring 111 may be formed on at least the top surface (front surface)of the base body, or may be also formed on the inside, the side surface,and/or the bottom surface (back surface) of the base body. Also, thewiring preferably has an element connection terminal part where thelight emitting element is mounted, an external connection terminal partto be connected to an external circuit, a lead wiring part that connectsthese terminal parts. The wiring can be constituted of copper, iron,nickel, tungsten, chromium, aluminum, silver, gold, titanium, palladium,rhodium, or an alloy of any of these. The wiring may be a single-layeror a multi-layer of metals or alloys. In particular, copper or a copperalloy is preferred from the viewpoint of the heat dissipation. Further,a layer formed of silver, platinum, aluminum, rhodium, gold, or an alloyof any of these may be provided on the surface layer of the wiring fromthe viewpoint of the wettability of the bonding member and/or the lightreflectivity.

Base Body

When the substrate is a rigid substrate, the base body 151 can beconstituted by using a resin or a fiber-reinforced resin, ceramics,glass, metal, paper, and the like. Examples of the resin or thefiber-reinforced resin may include epoxy, glass epoxy, bismaleimidetriazine (BT), polyimide. Examples of the ceramics may include aluminumoxide, aluminum nitride, zirconium oxide, zirconium nitride, titaniumoxide, titanium nitride, a mixture of any of these, and the like.Examples of the metal may include copper, iron, nickel, chromium,aluminum, silver, gold, titanium, an alloy of any of these. When thesubstrate is a flexible substrate, the base body can be constituted byusing polyimide, polyethylene terephthalate, polyethylene naphthalate,liquid crystal polymer, cycloolefin polymer. Among these substrates, itis especially preferable to use a substrate having a physical propertyclose to the coefficient of linear expansion of the light emittingelement.

Conductive Adhesive Member

As for the conductive adhesive member 20, at least one of: a bump suchas a gold bump, a silver bump, or a copper bump; a metal pastecontaining metal powder such as silver powder, gold powder, copperpowder, platinum powder, aluminum powder, or palladium powder and aresin binder; solder such as tin-bismuth-based solder, tin-copper-basedsolder, tin-silver-based solder, or gold-tin-based solder; and brazingfiller metal such as low melting point metal; can be used.

Light Guide Member

The light guide member is a member 40 of bonding the light emittingelement to the wavelength converting member, and guiding the lightemitted from the light emitting element to the wavelength convertingmember. Examples of the matrix of the light guide member may include asilicone resin, an epoxy resin, a phenol resin, a polycarbonate resin,an acrylic resin, and a modified resin of any of these. Among others, asilicone resin and a modified silicone resin are preferred since theheat resistance and the light resistance are excellent. Specificexamples of the silicone resin may include a dimethyl silicone resin, aphenylmethyl silicone resin, and a diphenyl silicone resin. Further, theresin constituting the light guide member may contain a filler similarto that of the wavelength converting member.

Light Reflective Covering Member

In the light reflective covering member 701, the light reflectance atthe light emission peak wavelength of the light emitting element ispreferably 70% or more, more preferably 80% or more, even morepreferably 90% or more, from the viewpoint of the forward lightextraction efficiency. The color of the covering member is preferablywhite. Thus, the covering member is preferably formed by containingwhite pigment in the resin. The covering member is once being a liquidstate before the curing. The covering member can be formed by transfermolding, injection molding, compression molding, potting.

Resin of Covering Member

Examples of the resin 75 of the covering member may include a siliconeresin, an epoxy resin, a phenol resin, a polycarbonate resin, an acrylicresin, and a modified resin of any of these. Among others, a siliconeresin and a modified silicone resin are preferred since the heatresistance and the light resistance are excellent. Specific examples ofthe silicone resin may include a dimethyl silicone resin, a phenylmethylsilicone resin, and a diphenyl silicone resin. Further, the resinconstituting the covering member may contain a filler similar to that ofthe wavelength converting member.

White Pigment

As for the white pigment 77, one kind of titanium oxide, zinc oxide,magnesium oxide, magnesium carbonate, magnesium hydroxide, calciumcarbonate, calcium hydroxide, calcium silicate, magnesium silicate,barium titanate, barium sulfate, aluminum hydroxide, aluminum oxide, andzirconium oxide can be used alone, or two or more kinds thereof can beused in combination. The shape of the white pigment is not particularlylimited. The shape may be an undefined shape or a crushed shape, and ispreferably a spherical shape from the viewpoint of the fluidity. Theparticle diameter of the white pigment may be, for example, in a rangeof 0.1 μm or more and 0.5 μm or less, but in order to enhance theeffects of light reflecting and covering, a smaller particle diameter ismore preferred. The content of the white pigment in the light reflectivecovering member can be appropriately selected, but from the viewpointsof the light reflectivity, the viscosity in a liquid state, and thelike, the content is preferably in a range of 10% by mass or more and80% by mass or less, more preferably in a range of 20% by mass or moreand 70% by mass or less, even more preferably in a range of 30% by massor more and 60% by mass or less, still more preferably in a range of 50%by mass or more and 65% by mass or less, relative to the total amountthat is 100% by mass of the covering member.

Method for Producing Light Emitting Device

The method for producing a light emitting device contains a first stepof subjecting a light emitting element 30 on a substrate 101 to aflip-chip mounting, a second step of bonding a first main surface of awavelength converting member 50 onto the light emitting element 30 via alight guide member 40, a third step of cutting the side surfaces of thewavelength converting member 50, a fourth step of covering the sidesurfaces of the light emitting element 30 and the wavelength convertingmember 50 with a light reflective covering member 701 to thereby formthe covering member 701 on the substrate 101, and a fifth step ofcutting the substrate 101 and the covering member 701 to thereby form anindividual light emitting device 100. Specifically, a light emittingdevice can be produced according to the method described in JapaneseUnexamined Patent Publication No. 2017-188592.

EXAMPLES

The present invention is hereunder specifically described by referenceto the following Examples. The present invention is not limited to theseExamples.

Production of Wavelength Converting Member

Example 1

A β-SiAlON fluorescent material having a circularity of 0.715 was usedas a second fluorescent material. A Mn⁴⁺-activated potassiumfluorosilicate fluorescent material was used as a first fluorescentmaterial. A phenylmethyl silicone resin was used as a resin. A siliconoxide nanop article having a particle diameter in a range of 10 nm ormore and 500 nm or less was used as a filler. 27 parts by mass of theβ-SiAlON fluorescent material, 63 parts by mass of the Mn⁴⁺-activatedpotassium fluorosilicate fluorescent material (the total amount of thefirst fluorescent material and the second fluorescent material was 90parts by mass), and 0.4 parts by mass of the silicon oxide nanoparticlewere mixed to 100 parts by mass of the resin, and the resin was cured tothereby form a sheet-shaped first wavelength converting layer. Thethickness of the first wavelength converting layer was 145 μm. Aphenylmethyl silicone was used as a resin to form a translucent layerhaving a thickness of 40 μm. The first wavelength converting layer andthe translucent layer were bonded using an epoxy resin as a light guidemember, thereby producing a rectangular-shaped chip wavelengthconverting member having a size of 185 μm thickness, 1.21 mm width(crosswise), and 0.16 mm depth.

Examples 2 to 4

A wavelength converting member was produced by the same method as inExample 1 except that a β-SiAlON fluorescent material having acircularity of each of Examples 2 to 4 described in Table 1 was used asa second fluorescent material.

Comparative Example 1

A wavelength converting member was produced by the same method as inExample 1 except that a β-SiAlON fluorescent material having acircularity of 0.674 was used as a second fluorescent material.

Light Emitting Device

A light emitting device 100 similar to the one shown in FIG. 5 or FIG. 6was produced by using the wavelength converting member of each ofExamples and Comparative Example 1. Specifically, a side surfaceemission-type light emitting device having a size of 1.8 mm width(crosswise), 0.32 mm thickness (lengthwise), and 0.70 mm depth wasproduced.

The chip substrate 101 had a size of 1.8 mm width (crosswise), 0.32 mmthickness (lengthwise), and 0.36 mm depth. The base body 151 was arectangular-shaped chip made of a BT resin (for example, HL832NSF typeLCA, manufactured by Mitsubishi Gas Chemical Company, Inc.). A pair ofpositive and negative wirings 111 was formed by laminating copper,nickel, and gold from the base body 151 side. The pair of positive andnegative wirings 111 contained an element connection terminal part thatwas formed at a center area in the lateral direction on the frontsurface of the base body 151, a lead wiring part, and externalconnection terminal parts that were formed from the left and rightterminal parts on the front surface of the base body 151 to the left andright terminal parts on the back surface via the side surfaces, and wereexposed from the left and right of the covering member 701 to bedescribed below. Here, the element connection terminal part contained acopper-layered bump having a depth of 0.04 mm. One light emittingelement 30 was flip-chip mounted on the element connection terminal partof the pair of positive and negative wirings 111 via the conductiveadhesive member 20. The light emitting element 30 was arectangular-shaped LED chip having a size of 1.1 mm width (crosswise),0.2 mm thickness (lengthwise), and 0.12 mm depth, capable of emittingblue light (light emission peak wavelength of 452 nm), in which ann-type nitride semiconductor layer, an active layer, and a p-typenitride semiconductor layer were sequentially laminated on a sapphiresubstrate. The conductive adhesive member 20 was a gold-tin-based solder(Au:Sn=79:21) having a depth of 0.015 mm. The wavelength convertingmember 50 of each of Examples and Comparative Example was bonded on thelight emitting element 30 via the light guide member 40. The wavelengthconverting member 50 had a first main surface 51 a that was one surfaceof the first wavelength converting layer 51 and a second main surface 55b that was one surface of the translucent layer 55 on a side opposite tothe first main surface, and the first main surface 51 a that was onesurface of the first wavelength converting layer 51 was bonded to thelight emitting element 30 via the light guide member 40. The light guidemember 40 was a cured product made of a dimethyl silicone resin having adepth of 0.005 mm. The light reflective covering member 701 was formedon the front surface of the chip substrate 101 so as to surround wholeside circumference of the light emitting element 30 and the wavelengthconverting member 50. The covering member 701 had a size of 1.35 mmwidth (crosswise) and 0.32 mm thickness (lengthwise), and was formed bycontaining 60% by mass of titanium oxide as the white pigment 77 in theresin 75 that was a cured product made of a phenylmethyl silicone resin.The covering member 701 directly covered the side surfaces of the lightemitting element 30, the side surfaces of the light guide member 40, andthe side surfaces of the wavelength converting member 50. The frontsurface of the covering member 701 was formed to constitutesubstantially the same surface as the front surface of the wavelengthconverting member 50.

Average Particle Diameter According to FSSS Method

The average particle diameter D2 of the β-SiAlON fluorescent materialused in each of Examples and Comparative Example; and the averageparticle diameter D1 of the Mn⁴⁺-activated fluoride fluorescent materialas a first fluorescent material used in each of Examples and ComparativeExample were measured according to the FSSS method. Specifically, usinga Fisher Sub-Sieve Sizer Model 95 (manufactured by Fisher ScientificInc.), each of the β-SiAlON fluorescent materials and the Mn⁴⁺-activatedfluoride fluorescent materials was sampled in an amount of 1 cm³ underan environment at a temperature of 25° C. and a humidity of 70% RH, andpacked in a dedicated tubular container. Then, a dry air flow wasintroduced therein under a constant pressure to read a specific surfacearea of the sample from the differential pressure, and thus the averageparticle diameter according to the FSSS method was calculated. Theresults are shown in Table 1.

Volume Average Particle Diameter Dm2 According to Laser DiffractionScattering

Particle Size Distribution Measuring Method

As for the β-SiAlON fluorescent material used in each of Examples andComparative Example, using a laser diffraction scattering particle sizedistribution measuring apparatus (Mastersizer 3000, manufactured byMalvern Instruments Ltd.), the volume average particle diameter (mediandiameter) Dm2 where the volume cumulative frequency from the smalldiameter side reached 50% was measured. The results are shown inTable 1. As for the β-SiAlON fluorescent material used in each ofExamples and Comparative Example, the particle diameter ratio D2/Dm2 ofthe average particle diameter D2, as determined according to the FSSSmethod, to the volume average particle diameter Dm2 was calculated. Theresults are shown in Table 1.

SEM Micrograph

Using a scanning electron microscope (SEM), SEM micrographs of theβ-SiAlON fluorescent materials used in Examples and Comparative Examplewere obtained. FIG. 8 shows an SEM micrograph of the β-SiAlONfluorescent material used in Example 1, FIG. 9 shows an SEM micrographof the β-SiAlON fluorescent material used in Example 3, and FIG. 10shows an SEM micrograph of the β-SiAlON fluorescent material used inComparative Example 1.

Circularity

The circularity of the β-SiAlON fluorescent material used in each ofExamples and Comparative Example was determined by: randomly selecting5,000 particles from the photographed image by the observation using anoptical microscope; measuring a projected area (S (m²)) and a peripherallength (L (m)) of each of the selected particles using an imageprocessing software (Morphologi G3S, manufactured by Malvern InstrumentsLtd.); calculating a circularity of each of the particles according tothe following formula (1); and averaging the calculated circularities.Circularity=4πS/L²  (1)Aspect Ratio

The aspect ratio of the β-SiAlON fluorescent material used in each ofExamples and Comparative Example was determined by: randomly selecting5,000 particles from the photographed image by the observation using anoptical microscope; measuring a long diameter and a short diameter ofeach of the selected particles using an image processing software(Morphologi G3S, manufactured by Malvern Instruments Ltd.); calculatinga ratio (short diameter/long diameter) of the short diameter to the longdiameter as the aspect ratio of each of the particles; and averaging thecalculated ratios.

Standard Deviation xσ, yσ of Chromaticity (x, y)

With respect to a plurality of the light emitting devices of each ofExamples and Comparative Example, the chromaticity x, y was measuredusing an optical measurement system combining a multichannelspectrometer and an integrating sphere. The chromaticities x, y of thelights emitted from a plurality of the light emitting devices and thestandard deviations xσ, yσ of the chromaticities x, y were determinedfor each Example and Comparative Example. Specifically, thechromaticities x, y of 3,700 light emitting devices were measured foreach Example and Comparative Example, and the standard deviations xσ ofthe chromaticities x and the standard deviations yσ of thechromaticities y were determined. It indicates that the smaller thevalues of the standard deviation xσ of the chromaticity x and thestandard deviation yσ of the chromaticity y in the light emitting deviceof each of Examples and Comparative Example can be suppressed the colortone variation among the light emitting devices, and thus a more desiredcolor tone can be changed. The results are shown in Table 1.

TABLE 1 First Fluorescent Material Mn⁴⁺-activated Fluoride FluorescentSecond Fluorescent Material Material β-SiAlON Fluorescent Material LightEmitting Average Particle Average Particle Volume Device Diameter D1Diameter D2 Average Particle Standard Deviation According to Accordingto Particle Diameter xσ, yσ of FSSS Method Aspect FSSS Method DiameterDm2 Ratio Chromaticity (x, y) (μm) Circularity Ratio (μm) (μm) D2/Dm2 xσyσ Comparative 9.0 0.674 0.619 13.0 19.5 0.667 0.0011 0.0045 Example 1Example 1 9.0 0.715 0.705 12.4 15.8 0.785 0.0011 0.0044 Example 2 9.00.752 0.688 9.7 12.6 0.770 0.0012 0.0040 Example 3 9.0 0.744 0.718 9.912.2 0.811 0.0010 0.0036 Example 4 9.0 0.811 0.721 9.6 12.1 0.793 0.00090.0030

As for the β-SiAlON fluorescent material contained in the wavelengthconverting member of the light emitting device in each of Examples 1 to4, the circularity was 0.7 or more, and the volume average particlediameter was in a range of 12.1 μm or more and 15.8 μm or less. Thecolor tone variation of the β-SiAlON fluorescent material contained inthe wavelength converting member of the light emitting device in each ofExamples 1 to 4 was suppressed as compared with that of the β-SiAlONfluorescent material contained in the wavelength converting member ofthe light emitting device in Comparative Example 1, and thus theproduction yield could be improved as compared with the light emittingdevice of Comparative Example 1. The circularity of the β-SiAlONfluorescent material contained in the wavelength converting member ofthe light emitting device in each of Examples 1 to 4 was 0.7 or more,that is, the nearly circular β-SiAlON fluorescent material was containedtherein. The standard deviation yσ of the chromaticity y, which dependedon the color tone of the β-SiAlON fluorescent material, in the lightemitting device of each of Examples 1 to 4 was smaller than that in thelight emitting device of Comparative Example 1. From these results, itcould be considered that the fluorescent material was uniformlydispersed in the resin to be uniformly arranged in the wavelengthconverting member, the light emitted from the light emitting elemententered from a substantially uniform surface direction with respect tothe β-SiAlON fluorescent material, and the change in chromaticity causedby entering the excitation light from various surface directions wassuppressed, so that a desired color tone could be obtained. The β-SiAlONfluorescent material contained in the wavelength converting member ofthe light emitting device in each of Example 4 had the circularity of0.8 or more, and β-SiAlON fluorescent material had a shape closer to acircle. Therefore. The light emitting device of Example 4 has thesmaller standard deviation yσ than the light emitting devices ofExamples 1 to 3. Further, the fluorescent material contained in thewavelength converting member of the light emitting device in each ofExamples 1 to 4 was uniformly dispersed in the resin to be uniformlyarranged in the wavelength converting member. Thereby, inconvenientbehaviors, which occurred at the time of cutting the sheet-shapedwavelength converting member, such as sticking out of the fluorescentmaterial to the outside from the end surface of the cut wavelengthconverting member and strain generated on the wavelength convertingmember, could be avoided.

The wavelength converting member according to one embodiment of thedescription and the light emitting device using the same can be utilizedfor backlight sources of liquid crystal displays, various kinds oflighting fixtures, various kinds of display devices such asadvertisements and destination guides, projector devices, and the like.

The invention claimed is:
 1. A light emitting device, comprising asheet-shaped wavelength converting member and a light emitting elementhaving a light emission peak wavelength in a range of 400 nm or more and480 nm or less, wherein the sheet-shaped wavelength converting membercomprising a first wavelength converting layer containing: a firstfluorescent material having a light emission peak wavelength in a rangeof 620 nm or more and 660 nm or less; a second fluorescent materialhaving a light emission peak wavelength in a range of 510 nm or more and560 nm or less; and a resin, wherein an average particle diameter, asmeasured according to a Fisher Sub-Sieve Sizer method, of the firstfluorescent material is in a range of 2 μm or more and 30 μm or less,wherein the second fluorescent material comprises a β-SiAlON fluorescentmaterial, a circularity of the β-SiAlON fluorescent material is 0.7 ormore, and a volume average particle diameter, as measured according to alaser diffraction scattering particle size distribution measuringmethod, of the β-SiAlON fluorescent material is in a range of 2 μm ormore and 30 μm or less, and a ratio of an average particle diameter ofthe β-SiAlON fluorescent material, as measured according to the FisherSub-Sieve Sizer method, to the volume average particle diameter of theβ-SiAlON fluorescent material, as measured according to the laserdiffraction scattering particle size distribution measuring method, is0.67 or more, wherein a thickness of the first wavelength convertinglayer is in a range of 50 μm or more and 200 μm or less, and wherein thesheet-shaped wavelength converting member has a first main surface thatis one surface of the first wavelength converting layer, and a secondmain surface on a side opposite to the first main surface, and the firstmain surface is bonded to the light emitting element.
 2. A lightemitting device, comprising a sheet-shaped wavelength converting memberand a light emitting element having a light emission peak wavelength ina range of 400 nm or more and 480 nm or less, wherein the sheet-shapedwavelength converting member comprising: a second wavelength convertinglayer containing a first fluorescent material having a light emissionpeak wavelength in a range of 620 nm or more and 660 nm or less and afirst resin; and a third wavelength converting layer containing a secondfluorescent material having a light emission peak wavelength in a rangeof 510 nm or more and 560 nm or less and a second resin, wherein anaverage particle diameter, as measured according to a Fisher Sub-SieveSizer method, of the first fluorescent material is in a range of 2 μm ormore and 30 μm or less, wherein the second fluorescent materialcomprises a β-SiAlON fluorescent material, a circularity of the β-SiAlONfluorescent material is 0.7 or more, and a volume average particlediameter, as measured according to a laser diffraction scatteringparticle size distribution measuring method, of the β-SiAlON fluorescentmaterial is in a range of 2 μm or more and 30 μm or less, and a ratio ofan average particle diameter of the β-SiAlON fluorescent material, asmeasured according to the Fisher Sub-Sieve Sizer method, to the volumeaverage particle diameter of the β-SiAlON fluorescent material, asmeasured according to the laser diffraction scattering particle sizedistribution measuring method, is 0.67 or more, wherein a thickness ofeach of the second wavelength converting layer and the third wavelengthconverting layer is in a range of 10 μm or more and 150 μm or less,wherein the sheet-shaped wavelength converting member has a first mainsurface that is one surface of the third wavelength converting layer anda second main surface on a side opposite to the first main surface, andthe first main surface is bonded to the light emitting element, andwherein the second wavelength converting layer and the third wavelengthconverting layer are bonded together.
 3. The light emitting deviceaccording to claim 1, wherein an aspect ratio of the β-SiAlONfluorescent material is 0.62 or more.
 4. The light emitting deviceaccording to claim 2, wherein an aspect ratio of the β-SiAlONfluorescent material is 0.62 or more.
 5. The light emitting deviceaccording to claim 1, wherein the first fluorescent material comprises:a Mn⁴⁺-activated fluoride fluorescent material; a fluorescent materialcontaining an Eu²⁺-activated silicon nitride containing at least oneelement selected from Sr and Ca, and Al; and at least one fluorescentmaterial containing an Eu²⁺-activated aluminum nitride containing atleast alkaline earth metal element and at least one alkali metalelements, and wherein the second fluorescent material further comprises:a chlorosilicate-based fluorescent material; a Mn²⁺-activated aluminatefluorescent material containing at least one alkaline earth metalelement selected from the group consisting of Ba, Sr, and Ca; and atleast one γ-AlON fluorescent material.
 6. The light emitting deviceaccording to claim 2, wherein the first fluorescent material comprises:a Mn²⁺-activated fluoride fluorescent material; a fluorescent materialcontaining an Eu²⁺-activated silicon nitride containing at least oneelement selected from Sr and Ca, and Al; and at least one fluorescentmaterial containing an Eu²⁺-activated aluminum nitride containing atleast one alkaline earth metal element and at least one alkali metalelement, and wherein the second fluorescent material further comprises:a chlorosilicate-based fluorescent material; a Mn²⁺-activated aluminatefluorescent material containing at least one element selected from thegroup consisting of Ba, Sr, and Ca; and at least one γ-AlON fluorescentmaterial.
 7. The light emitting device according to claim 1, wherein amass ratio of the resin contained in the first wavelength convertinglayer to a total of the first fluorescent material and the secondfluorescent material falls within a range of 100:50 to 100:260.
 8. Thelight emitting device according to claim 2, wherein a mass ratio of thefirst resin contained in the second wavelength converting layer to thefirst fluorescent material falls within a range of 100:50 to 100:260,and a mass ratio of the second resin contained in the third wavelengthconverting layer to the second fluorescent material falls within a rangeof 100:50 to 100:150.
 9. The light emitting device according to claim 1,wherein the sheet-shaped wavelength converting member further comprisesa translucent layer containing no fluorescent material.
 10. The lightemitting device according to claim 2, wherein the sheet-shapedwavelength converting member further comprises a translucent layercontaining no fluorescent material.
 11. The light emitting deviceaccording to claim 10, wherein the second wavelength converting layer islocated between the translucent layer and the third wavelengthconverting layer, and wherein the second wavelength converting layercomprises a Mn⁴⁺-activated fluoride fluorescent material.
 12. The lightemitting device according to claim 1, wherein the resin is a siliconeresin or an epoxy resin.
 13. The light emitting device according toclaim 2, wherein at least one of the first resin and the second resin isa silicone resin or an epoxy resin.
 14. The light emitting deviceaccording to claim 9, wherein at least one of the first wavelengthconverting layer and the translucent layer comprises a filler, whereinthe filler is at least one selected from the group consisting of siliconoxide, zirconium oxide, titanium oxide, zinc oxide, and aluminum oxide.15. The light emitting device according to claim 10, wherein at leastone of the second wavelength converting layer, the third wavelengthconverting layer, and the translucent layer comprises a filler, whereinthe filler is at least one selected from the group consisting of siliconoxide, zirconium oxide, titanium oxide, zinc oxide, and aluminum oxide.